Volcanoes
Applications
Volcanoes are vents or fissures in the Earth’s crust through which lava, tephra, and gases escape from magma chambers beneath the surface. Understanding volcanic activity is vital for disaster monitoring and response, climate modelling, and impact assessment. Satellite observations are a critical tool for monitoring the more than 1,300 active and above-sea volcanoes that pose potential threats to both the environment and society. Satellites can remotely detect seismic activity to predict eruptions and as well as monitor their impacts on the atmosphere and surface of the planet.
Volcanoes are commonly found along the boundaries of tectonic plates. At divergent boundaries where plates pull apart, new paths for hot magma to reach the surface are created, which can result in the formation of volcanic vents. At convergent boundaries where plates are moving together, molten rock from the subducting plate can well up, creating magma pools that fuel volcanic activity on the surface. Volcanoes can also form away from plate boundaries, in what is known as hotspot or intraplate volcanism. This form of volcanic vent forms above a column of superheated magma known as a mantle plume, as the heat of the plume causes a thinning of the crust, allowing volcanic activity at the surface. 4) 7) 13) 14)
Volcanoes are broadly classified into three categories:
- Active volcanoes have a history of eruption and are likely to erupt again.
- Dormant volcanoes do not have a recent eruption history but have the potential for future activity.
- Extinct volcanoes have a history of eruption, but are no longer capable of eruption.
Volcanic eruptions vary significantly in their scale and impact. An eruption is broadly defined as the expulsion of gases, rock fragments (tephra), or molten lava from a vent on the Earth’s surface. Due to the relative buoyancy of magma compared to the surrounding solid rock, it rises to Earth’s surface from beneath the crust, collecting in magma pools. As more magma and gases collect, the pressure within the pools increases. Eventually this results in cracks forming in the crust, allowing the pressure to be released in a volcanic eruption. Depending on the makeup and consistency of the magma within a pool, this can result in a violent and explosive eruption, or a less destructive lava flow. Magma that has a higher silica content tends to be thicker, thus preventing gases from easily escaping. As a result, higher silica magma results in more explosive eruptions, as it allows more pressure to build up beneath the surface. 4) 7) 13) 14)
Space-based measurements aid in the prediction, monitoring, and impact assessment of volcanic events. The deformation of a volcano’s ground surface, caused by the build up of magma, gases, and pressure beneath the surface is an indicator of volcanic activity. Satellite-based measurements of topographic differencing can identify areas with significant ground deformation, supporting the forecasting of an eruption. This ground level monitoring is primarily achieved through interferometric synthetic aperture radar (InSAR), which can be used to produce ground deformation maps. This can replace in-situ techniques such as ground GPS receivers, which have limited spatial coverage. 2) 3) 5) 11) 13) 14)
Spaceborne thermal infrared (TIR) sensors can detect temperature changes caused by lava flows or eruptions and image the progression of volcanic activity. Geostationary satellites, such as the GOES, Meteosat and Himawari series, allow for continuous observation of single scenes, allowing for the rapid identification of volcanic activity and continuous monitoring of active volcanoes. Meanwhile, thermal imaging satellites in Low Earth Orbit (LEO), such as the Landsat satellites, provide higher spatial resolution thermal imagery but typically at a lower temporal resolution. 2) 11)
Satellite monitoring of ash and tephra clouds produced by volcanic eruptions can be used in climatological impact assessment following an eruption, and to inform regulatory bodies for the closure of air spaces. Both Geostationary and LEO satellites can carry sensors capable of detecting ash, sulphur dioxide (SO2), and climatological temperature anomalies used for ash cloud analyses and air quality assessments. 2) 3) 4) 5) 12)
Example Products
MODIS Thermal Alert System
The Moderate Resolution Imaging Spectrometer (MODIS) Thermal Alert System is an automated detection programme that uses data from NASA’s Terra and Aqua satellites to identify active fires and other thermal anomalies, including volcanic activity. The MODIS MOD14/MYD14 Fire and Thermal Anomalies algorithm identifies thermal anomalies with global coverage every two days. 1) 8)
The Thermal Alert System can be used to identify activity at known volcanic sites using data received from MODIS. MODIS is an optomechanical imaging spectrometer that images in 36 bands between 0.4 and 14.5 µm (21 bands within 0.4-3.0 µm range, 15 bands within 3-14.5 µm range). It aims, among other objectives, to determine surface temperature at 1 km spatial resolution with accuracies of 0.2 K for ocean and 1 K for land. The system uses a threshold based algorithm to determine hotspots, with the standard threshold set at 310 K (36.85°C). This threshold can change depending on the observed temperature of surrounding pixels and other factors such as regional climates and times of day. 1) 8) 9)
Interferometric SAR Maps
Interferometric SAR (InSAR) compares parallel SAR acquisitions of the same area to determine surface deformation over time. When surface deformation occurs, this is seen as a relative phase shift in the backscatter received by the satellite when compared to a parallel acquisitions over the same area. InSAR sensors are capable of detecting ground shifts on the millimetre scale, making them highly applicable for monitoring seismic and volcanic activity. 3) 5) 6) 11)
Unwrapped interferograms are highly relevant to the study and prediction of volcanic activity. They can identify ground uplift, an indicator of an impending eruption, as magma accumulates beneath the surface, as well as quantify ground deformation, aiding estimation of how much magma is moving and the likelihood of an eruption. 3) 5) 6)
Total Column Ash Content
Atmospheric profiling is used to support post-eruption environmental impact assessments, supporting disaster recovery efforts. Measurements of total column ash content is conducted through three primary methods: IR absorption and scattering, UV absorption, and multispectral comparisons.
Volcanic ash absorbs and scatters TIR radiation at distinct wavelengths against common atmospheric components like water vapour. Contrast in TIR observations is apparent in the 10 - 12 µm range, allowing the detection of ash clouds. However, IR absorption cannot accurately detect fine ash particles or differentiate ash and ice clouds at high altitudes.
The application of Ultraviolet (UV) remote sensing makes use of a similar principle, as volcanic ash absorbs UV light in shorter wavelengths (320 - 380 nm). Through UV absorption data, an Absorbing Aerosol Index (AAI) can be calculated, which is correlated with ash concentration. However, UV remote sensing is only available in daylight and is easily impacted by other absorbing aerosols such as smoke or dust. 11) 12)
Multispectral and Hyperspectral imaging offer a reliable method of identifying and quantifying ash clouds and their properties. Hyperspectral imaging facilitates observation across a wide spectral swath and many narrow, contiguous spectral bands. The interaction of ash clouds with various wavelengths of light provides more information than single-band imagery. The key interactions observed are absorption, scattering and emission. Examination of these characteristics across a range of bands provides differentiation of ash clouds from other atmospheric components, detection of ash cloud content, estimation of cloud density and depth, and tracking of high altitude fine ash particles that cannot be detected by traditional IR sensors. 10) 11) 12)
In the News
Satellite-based volcano monitoring continues to play an essential role in tracking volcanic activity, mapping lava flows, monitoring ash clouds, and supporting early warning systems.
Mount Etna Eruption: June 2025
Mount Etna, located on the island of Sicily, is the highest active volcano in Europe and usually erupts a few times a year. On 2 June 2025, Mt Etna erupted in what the Italian National Institute of Geophysics and Volcanology (INGV) noted was the largest eruption since 2014, with preliminary observations indicating the eruption resulted from "a collapse of material from the northern flank of the south-east crater”. As of 5 June, the full scale of the eruption is still under assessment, but no significant damage or injuries are expected. Experts are continuing to monitor the volcano’s activity closely. 15)
The Copernicus Sentinel-2C mission captured dramatic images of Mount Etna just minutes after the eruption began, showing a thick column of ash and smoke rising up to 6,500 metres into the atmosphere. 17)
Related Missions
Copernicus Sentinel-5
Sentinel-5P is an atmospheric monitoring satellite launched in October 2017 by the European Commission's Copernicus program, in partnership with ESA and EUMETSAT. The onboard Tropospheric Monitoring Instrument (TROPOMI) can detect and measure SO2 emissions, which are commonly released during volcanic eruptions. This allows the tracking of volcanic gas plumes and the monitoring of potential air quality impacts, as well as estimations of eruption magnitude based on SO2 emission levels.
Sentinel-5, also known as UVNS (Ultra-violet Visible Near-infrared Shortwave-infrared spectrometer), is a pushbroom spectrometer instrument that will monitor the chemical composition of the atmosphere, and thus can be applied to detection of SO2 plumes and the atmospheric effects of volcanic activity.
Read more: Sentinel-5, Sentinel-5P
Landsat-9 and -9
Landsat 8, launched in February 2013 by NASA, provides high resolution optical and thermal infrared imaging of the Earth’s surface. The onboard Thermal Infrared Sensor (TIRS) produces TIR imagery which can be used to monitor hotspots, lava flows, and crater temperatures for early warning signs of eruptions. Landsat 9 also captures visible and IR imagery with the Operational Land Imager (OLI) which can be used to monitor lava flows, but can also be applied in conjunction with InSAR data to monitor ground deformation, an indicator of volcanic activity. Landsat-9, launched in September 2021, carries updated and improved versions of these instruments, the Thermal Infrared Sensor 2 (TIRS-2) and Operational Land Imager 2 (OLI-2), with identical applications in volcanic monitoring.
Himawari-8 and -9
Himawari-9, launched in 2016, is a geostationary weather and environmental satellite positioned over the Asia-Pacific region operated by the Japan Meteorological Agency (JMA). It carries the Advanced Himawari Imager (AHI), which provides multi-purpose imagery in 16 channels across VIS, NIR, SWIR, MWIR and TIR spectral bands (from ~ 0.43 to ~13.4 µm). Imagery provided by AHI can be used for ash plume tracking and detection, as well as estimates of ash cloud height and total column ash content. As a geostationary satellite, Himawari-9 can also provide constant monitoring of volcanic activity. Himawari-8, prior to its replacement by Himawari-9 in November 2022, served the same roles in volcanic monitoring and carried the same instrument.
GOES-R Series
The GOES-R series, first launched with GOES-16 in 2016, is a series of four geostationary weather and environmental satellites positioned over North America, owned and operated by NOAA and NASA. The Advanced Baseline Imager (ABI) it carries is a multispectral imager which aims to provide high-resolution imagery and radiometric information of the Earth's surface, the atmosphere and the cloud cover. GOES-R imagery can be applied to detection and tracking of volcanic ash and gas clouds, using IR channels provided by ABI. It can also be used for continuously monitoring thermal anomalies and tracking lava flows, as a geostationary satellite.
MODIS (Terra and Aqua)
Terra and Aqua, launched in 1999 and 2002 respectively, are low Earth orbiting (LEO) satellites that provide data on Earth’s atmosphere, land surface, ocean, and cryosphere. Both satellites carry the Moderate Resolution Imaging Spectrometer (MODIS), which provides thermal anomaly data to the MODIS Thermal Alert System. Both satellites are owned and operated by NASA.
AVHRR
AVHRR (Advanced Very High Resolution Radiometer) is a multispectral imaging radiometer carried on the NOAA POES series and MetOp-A, -B and -C. AVHRR data has a range of applications from land and sea surface temperature, cloud cover, and soil moisture content, as well as atmospheric aerosol and ash monitoring, which are used to monitor volcanic eruptions.
EnMAP
EnMap (Environmental Monitoring and Analysis Program) is a German mission which collects hyperspectral imagery of Earth’s atmosphere and surface. The mission was launched in 2022 and is operated by the German Aerospace Centre (DLR). The hyperspectral imager it carries can be used to monitor atmospheric volcanic ash.
CALIPSO
Launched in April 2006, CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) was a joint NASA/CNES mission for cloud and aerosol observation. It carried the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument, which acquired vertical column profiles of aerosol and cloud distribution, and was used to track volcanic ash plumes after eruptions. It also carried an Imaging Infrared Radiometer (IIR) and a Wide Field Camera (WFC).
Meteosat Third Generation
Meteosat Third Generation (MTG) is a collaborative ESA/EUMETSAT weather forecasting mission. The Flexible Combined Imager carried by MTG series satellites enables cloud and aerosol detection, as well as localised fire event monitoring. Aerosol monitoring can be used to track volcanic ash clouds and gases released in eruptions, while localised fire monitoring is applicable in identifying potential lava flows in known volcanically active areas.
Sentinel-3
Sentinel-3 is an ESA radar imaging mission consisting of two satellites. Its Sea and Land Surface Temperature Radiometer (SLSTR) can be used for monitoring lava flows and other volcanic activity. Sentinel-3 satellites also carry a SAR Altimeter (SRAL), Ocean and Land Colour Imager (OLCI), and a Microwave Radiometer (MWR).
MetOp-SG
The MetOp-SG mission is a series of six meteorological satellites, developed by ESA and EUMETSAT. Satellites in the series carry a Meteorological Imager (METImage) and Multi-viewing, Multi-channel, Multi-polarization Imager (3MI), which can be used to monitor aerosols and cloud microphysical characteristics, including volcanic plume observations. Additionally, the Infrared Atmospheric Sounding Interferometer–New Generation (IASI-NG) instrument conducts total profile observations, allowing observation of total column ash content.
References
1) CNR IREA, “Differential Synthetic Aperture Radar Interferometry.” URL: http://www.irea.cnr.it/en/index.php?option=com_k2&view=item&id=77:differential-synthetic-aperture-radar-interferometry&Itemid=139
2) Committee on Earth Observation Satellites, “CEOS Volcano Pilot: Using Satellite Data to Monitor Remote Volcanoes” URL: https://ceos.org/home-2/ceos-volcano-pilot-using-satellite-data-to-monitor-remote-volcanoes/
3) Earle, Steven. “7.1 Plate Tectonic Settings of Volcanism – Environmental Geology.” URL: https://environmental-geology-dev.pressbooks.tru.ca/chapter/plate-tectonic-settings-of-volcanism/
4) Gündüz, Halil İbrahim. “An Investigation of Volcanic Ground Deformation Using InSAR Observations at Tendürek Volcano (Turkey).”, 2 June 2023, URL: https://www.mdpi.com/2076-3417/13/11/6787
5) Geoscience Australia, “Interferometric Synthetic Aperture Radar.”,14 December 2017, URL: https://www.ga.gov.au/scientific-topics/positioning-navigation/geodesy/geodetic-techniques/interferometric-synthetic-aperture-radar
6) King, Chris. British Geological Survey, “How volcanoes form.” URL: https://www.bgs.ac.uk/discovering-geology/earth-hazards/volcanoes/how-volcanoes-form-2/
7) NASA Earthdata, “MODIS/Aqua Terra Thermal Anomalies/Fire locations 1km FIRMS NRT (Vector data).”, 1 March 2021, URL: https://www.earthdata.nasa.gov/data/catalog/lancemodis-mcd14dl-6.1nrt
8) NASA, “LANCE | FIRMS”, URL: https://firms.modaps.eosdis.nasa.gov/descriptions/FIRMS_MODIS_Firehotspots.html
9) NASA, “MODIS Web.” URL: https://modis.gsfc.nasa.gov/data/dataprod/mod14.php
10) NASA Technical Reports Server, “Ultraviolet Satellite Measurements of Volcanic Ash.”, 27 May 2016, URL: https://ntrs.nasa.gov/citations/20170003367
11) Petracca, Ilaria, et al., European Geosciences Union, “Volcanic cloud detection using Sentinel-3 satellite data by means of neural networks: the Raikoke 2019 eruption test case.”, 14 December 2022, URL: https://amt.copernicus.org/articles/15/7195/2022/
12) Schmidt, Laurie J., NASA Earthdata, “Sensing Remote Volcanoes.”, 28 July 2020, URL: https://www.earthdata.nasa.gov/news/feature-articles/sensing-remote-volcanoes
13) USGS, “Volcano Watch — Monitoring volcano movements with satellites | U.S. Geological Survey.” URL: https://www.usgs.gov/news/volcano-watch-monitoring-volcano-movements-satellites
14) Westby, Elizabeth G., and Lisa M. Faust. “How Do Volcanoes Erupt? | U.S. Geological Survey.” URL: https://www.usgs.gov/faqs/how-do-volcanoes-erupt
15)ESA, “Mount Etna erupts.” URL: https://www.esa.int/ESA_Multimedia/Images/2025/06/Mount_Etna_erupts
16) BBC Newsround, “Mount Etna eruption captured by satellites.” URL: https://www.bbc.co.uk/newsround/articles/crr71d0ww5vo
17) Universe Magazine, “Satellite photographs eruption of Mount Etna.” URL: https://universemagazine.com/en/satellite-photographs-eruption-of-mount-etna/?srsltid=AfmBOoo7ctOpPrDphrHcU25PPWE40AE3uFPdzwXkM66YzNDHlPsIib1d
18) Orbital Today, “Satellite images reveal Etna’s eruption and lava in stunning detail.” URL: https://orbitaltoday.com/2025/06/03/satellite-images-reveal-etnas-eruption-and-lava-in-stunning-detail/